1. Field of the Invention
The present invention relates to a seal, a system and a method for individually sealing electrical contacts in connectors and between mating connectors and, in particular, to such a system and method which maintains the electrical integrity of connection regardless of changing pressures.
2. Description of the Prior Art and Background
An electrical connector, including an insulation body, contacts and seals, in connecting one electronic component to another, must be constructed so as not to impair the quality or transmission of conveyed signals and, consequently, must be electrically secure from short circuiting and arcing, for example. Furthermore, since the signals to be transmitted will dictate the size of wire utilized in the connectors, the connectors must be capable of accommodating different sizes of wires, yet not fail in compromising the electrical integrity. Generally, electrical connectors are subject to failure at one of several points, at least where the cable enters each connector at its rear faces and where the contacts mate at the front face of the connectors. Such failure is caused by arcing and short circuiting between wire and/or contacts due to the fact that conductive fluids such as salt laden air, provide a conductive path which is capable of making electrical contact between adjacent cables and/or contacts.
To overcome these problems relating to arcing and short circuiting, one of two conventional methods have been utilized. A first conventional method provides a resilient, insulating wafer which is usually bonded to the wire or rear end of a rigid connector block. The wafer is apertured to permit insertion of a contact into the connector block and sealing means in the wafer engages the wire which is attached to the contact. To prevent possible deterioration of the bond between the wafer and the connector block upon repeated flexing of the wires, an additional rigid wire guide is bonded to the rubber wafer. Furthermore, the wafer and, in particular its sealing means, is subject to damage upon insertion of the contact through the wafer by the metal edges of the contact and contact insertion tools.
Also, it is conventional to utilize insulated wires of different diameters; however, it is not economically feasible to design a wafer for each combination of wire sizes. As a consequence, a standard sized wafer is used with the result that its holes will not be altogether suitable for all sizes of wire. Finally, a particular electrical connector may require the use of wires having a large diameter which, although adequately being sealed within individual holes of the wafer, expand the holes to such an extent that it eventually becomes extremely difficult, if not impossible, to insert the remaining wires into the connector body without damage to the rubber wafer, bond joints or connector body.
Even when this type of conventional connector block operates properly, its use results in a fairly high cost of materials, assembly, testing and replacement. Since such a connector requires at least two components, the cost of assembly is relatively high because at least one assembly operation is required along with complete bonding of the wafer to the connector block and electrical and seal testing thereof in order to prevent the possibility of electrical failure. If a defect in the bonding is found, it is often necessary to scrap the entire connector either because it is not possible to effect a repair without the destruction of the wafer or because it is too time consuming and expensive to make such a repair.
To overcome the aforementioned problems, another connector sealing scheme pots and encapsulates the wires and contacts into the wire side of the connector block with polyurethane or epoxy materials. While this method substantially eliminates these problems, its use results in a permanent fixture which prevents later removal or exchange of contacts in the event of required wiring changes or should contacts be or become faulty.
Other problems are associated with the interface seal between two mating connectors. This seal also comprises a resilient, insulating wafer with a plurality of holes therethrough so that a pin contact may engage with its corresponding socket contact. Because mating connectors must often be separated, it is not possible to bond one connector body to the other; therefore, the interface seal must be capable of sealing without benefit of potting or other bonding means, at least on both connector bodies. Conventionally, the two connector bodies with the seal therebetween are clamped together under great pressure to maintain sealing integrity. It has been determined that as much as 85 psi clamp pressure must be utilized to maintain a seal of 30 psi pressure. Unfortunately, even with such clamping pressures, these interface seals are still subject to failure, such as may arise because of misalignment of contacts.
In both cases with rear wire seals and interface seals, conventional apparatus is still subject to other problems arising from changes or differentials in pressure differential. For example, a connector may be moved from ground level to a higher atmosphere and back to ground or sea level, such as by an airplane. At higher atmospheres, atmospheric pressure drops and any fluids or gases within the connectors exhaust to stabilize its internal pressure with the external pressure. Upon return of the aircraft to ground level, the pressure external to the connector is greater than the internal pressure, thereby permitting contaminants to be drawn into the connector interior should the seal be inadequate. This problem becomes particularly oppressive near or on the ocean where salt deposits permit rapid deterioration of electrical integrity by short circuiting.
This problem becomes aggravated with the use of helically wound insulation which acts as a wick.